Down-regulation of argininosuccinate lyase induces hepatoma cell apoptosis through activating Bax signaling pathway

Serum urea concentration and risk of 16 site-specific cancers, overall cancer, and cancer mortality in individuals with metabolic syndrome: a cohort study

BACKGROUND

The relationship between serum urea concentration and cancer in patients with metabolic syndrome (MetS) remains unclear. This study aimed to investigate the association between serum urea concentration and 16 site-specific cancers, overall cancer incidence, and cancer mortality in individuals with MetS.

METHODS

We analysed the data of 108,284 individuals with MetS obtained from the UK Biobank. The Cox proportional hazards model was used to determine the association between serum urea concentration at recruitment and cancer. The Benjamini-Hochberg correction was used to account for multiple comparisons.

RESULTS

Over the median follow-up period of 11.86 years, 18,548 new incident cases of cancer were documented. There were inverse associations of urea concentration with overall cancer incidence, and the incidence of oesophageal and lung cancers, with respective hazard ratios (95% confidence intervals) [HR (95% CI)] for the highest (Q4) vs lowest (Q1) urea quartiles of 0.95 (0.91-0.99), 0.68 (0.50-0.92), and 0.76 (0.64-0.90). However, high serum urea concentrations increased the male prostate cancer risk (HR 1.15; 95% CI 1.02-1.30). Although the Cox model indicated a protective effect of higher urea levels against stomach (HR 0.67; 95% CI 0.45-0.98; p = 0.040; FDR 0.120) and colorectal cancer (HR 0.86; 95% CI 0.74-0.99; p = 0.048; FDR 0.123), no strong evidence of association was found after applying the Benjamin-Hochberg correction. Moreover, across the median follow-up period of 13.77 years for cancer mortality outcome, 5034 cancer deaths were detected. An "L-shaped" nonlinear dose-response relationship between urea concentration and cancer mortality was discovered (p-nonlinear < 0.001), and the HR (95% CI) for urea concentration Q4 vs Q1 was 0.83 (0.77-0.91).

CONCLUSIONS

Serum urea concentration can be considered as a valuable biomarker for evaluating cancer risk in individuals with MetS, potentially contributing to personalised cancer screening and management strategies.

From the Inside Out: Exposing the Roles of Urea Cycle Enzymes in Tumors and Their Micro and Macro Environments

Catabolic pathways change in anabolic diseases such as cancer to maintain metabolic homeostasis. The liver urea cycle (UC) is the main catabolic pathway for disposing excess nitrogen. Outside the liver, the UC enzymes are differentially expressed based on each tissue's needs for UC intermediates. In tumors, there are changes in the expression of UC enzymes selected for promoting tumorigenesis by increasing the availability of essential UC substrates and products. Consequently, there are compensatory changes in the expression of UC enzymes in the cells that compose the tumor microenvironment. Moreover, extrahepatic tumors induce changes in the expression of the liver UC, which contribute to the systemic manifestations of cancer, such as weight loss. Here, we review the multilayer changes in the expression of UC enzymes throughout carcinogenesis. Understanding the changes in UC expression in the tumor and its micro and macro environment can help identify biomarkers for early cancer diagnosis and vulnerabilities that can be targeted for therapy.

Association between serum urea concentrations and the risk of colorectal cancer, particularly in individuals with type 2 diabetes: A cohort study

Dysregulation of the urea cycle (UC) has been detected in colorectal cancer (CRC). However, the impact of the UC's end product, urea, on CRC development remains unclear. We investigated the association between serum urea and CRC risk based on the data of 348 872 participants cancer-free at recruitment from the UK Biobank. Multivariable Cox proportional hazards models were fitted to conduct risk estimates. Stratification analyses based on sex, diet pattern, metabolic factors (including body mass index [BMI], the estimated glomerular filtration rate [eGFR] and type 2 diabetes [T2D]) and genetic profiles (the polygenic risk score [PRS] of CRC) were conducted to find potential modifiers. During an average of 9.0 years of follow-up, we identified 3408 (1.0%) CRC incident cases. Serum urea showed a nonlinear relationship with CRC risk (P-nonlinear: .035). Lower serum urea levels were associated with a higher CRC risk, with a fully-adjusted hazard ratio (HR) of 1.26 (95% confidence interval [CI]: 1.13-1.41) in the first quartile (Q1) of urea, compared to the Q4. This association was largely consistent across subgroups of sex, protein diet, BMI, eGFR and CRC-PRSs (P-interaction >.05); however, it was stronger in the T2D, with an interaction between urea and T2D on both additive (synergy index: 3.32, [95% CI: 1.24-8.88]) and multiplicative scales (P-interaction: .019). Lower serum urea concentrations were associated with an increased risk of CRC, with a more pronounced effect observed in individuals with T2D. Maintaining stable levels of serum urea has important implications for CRC prevention, particularly in individuals with T2D.

Amino Acid-Metabolizing Enzymes in Advanced High-Grade Serous Ovarian Cancer Patients: Value of Ascites as Biomarker Source and Role for IL4I1 and IDO1

The molecular mechanisms contributing to immune suppression in ovarian cancer are not well understood, hampering the successful application of immunotherapy. Amino acid-metabolizing enzymes are known to contribute to the immune-hostile environment of various tumors through depletion of amino acids and production of immunosuppressive metabolites. We aimed to collectively evaluate the activity of these enzymes in high-grade serous ovarian cancer patients by performing targeted metabolomics on plasma and ascites samples. Whereas no indication was found for enhanced l-arginine or l-glutamine metabolism by immunosuppressive enzymes in ovarian cancer patients, metabolism of l-tryptophan by indoleamine 2,3-dioxygenase 1 (IDO1) was significantly elevated compared to healthy controls. Moreover, high levels of l-phenylalanine- and l-tyrosine-derived metabolites associated with interleukin 4 induced 1 (IL4I1) activity were found in ovarian cancer ascites samples. While l-tryptophan is a major substrate of both IDO1 and IL4I1, only its enhanced conversion into l-kynurenine by IDO1 could be detected, despite the observed activity of IL4I1 on its other substrates. In ascites of ovarian cancer patients, metabolite levels were higher compared to those in plasma, demonstrating the value of utilizing this fluid for biomarker identification. Finally, elevated metabolism of l-phenylalanine and l-tyrosine by IL4I1 correlated with disease stage, pointing towards a potential role for IL4I1 in ovarian cancer progression.

The context-specific roles of urea cycle enzymes in tumorigenesis

The expression of the urea cycle (UC) proteins is dysregulated in multiple cancers, providing metabolic benefits to tumor survival, proliferation, and growth. Here, we review the main changes described in the expression of UC enzymes and metabolites in different cancers at various stages and suggest that these changes are dynamic and should hence be viewed in a context-specific manner. Understanding the evolvability in the activity of the UC pathway in cancer has implications for cancer-immune cell interactions and for cancer diagnosis and therapy.